HESS 509 Atrial Fibrillation CHAPTER ELEVEN In atrial fibrillation (AF), chaotic and rapid atrial contractions cause an irregular ventricular response,. This impairs ventricular filling and cardiac output and thus can lead to a variety of symptoms: Fatigue Decreased exercise capacity Pre-syncope, or syncope, falls Stroke Basic Pathophysiology Atrial fibrillation is one of the most common cardiac arrhythmias, and it occurs more frequently with advancing age. It is believed to be caused by multiple reentrant circuits within the atria. Atrial fibrillation often occurs with other cardiovascular conditions, particularly chronic heart failure, cardiomyopathy, valvular disease, coronary artery disease, hypertension, and hyperthyroidism. Some of these disorders may be underlying causes of AF, and in some cases they may be manifestations of AF.

Atrial Fibrillation Management and Medications HESS 509 Atrial Fibrillation CHAPTER ELEVEN Management and Medications Medical management of AF primarily involves two basic approaches: Converting the heart back to normal sinus rhythm (convert the individual back to sinus rhythm through electrical cardioversion, radiofrequency ablation, or a surgical method - many individuals return to AF within 4 to 6 weeks.) Controlling the ventricular rate response [(Medicines used to control the ventricular rate in AF include Digoxin, β-blockers (e.g., propranolol, sotalol, metoprolol, atenolol, and Nondihydropyridine calcium channel blockers (e.g., diltiazem, verapamil)] AF patients are at a high risk for stroke and must be anticoagulated. The irregular heart rhythm leads to small eddies of blood that don’t flush through the chambers very well, which can lead to formation of a thrombus that can be ejected from the heart and cause a stroke. Antithrombotic therapy reduces the risk of stroke by up to ≈80%.

Atrial Fibrillation Effects on the Exercise Response HESS 509 Atrial Fibrillation CHAPTER ELEVEN Effects on the Exercise Response Patients with AF have a rapid, irregular ventricular rate. Heart rate is comparatively high at any level of exercise, in part to compensate for the diminished stroke volume Maximal heart rate tends to be higher, although there is variability in the maximal heart rate response (standard deviations up to 30 beats/min) The heart rate response is also affected by comorbid conditions commonly associated with AF (e.g., coronary artery disease, chronic heart failure) Stroke volume is reduced in AF (reduced atrial systolic function) Because of the variability in the diastolic filling period, determination of systolic blood pressure can be difficult and is poorly reproducible Exercise tolerance is generally reduced in AF - this reduction is typically about 20%, but it is highly dependent on the presence and extent of underlying heart disease

Atrial Fibrillation Effects of Exercise Training HESS 509 Atrial Fibrillation CHAPTER ELEVEN Effects of Exercise Training Insufficient scientific literature is available concerning the effects of exercise training specifically in people with AF (typically a comorbid condition - AF associated with CAD) The major concerns during exercise training are symptoms of AF due to inadequate medical management (rate control) Atrial fibrillation can be very difficult to endure. The trial of medical management, electrophysiology studies, and pacemaker adjustment sounds simple, but in practice it often takes months before there is successful and sustained rate control. Many patients with AF find this frustrating and can really benefit from an exercise specialist who can help them through this period

Atrial Fibrillation Recommendations for Exercise Testing HESS 509 Atrial Fibrillation CHAPTER ELEVEN Recommendations for Exercise Testing Maximal exercise testing can be safely used to measure the functional capability of individuals with AF Exercise testing is also helpful in determining the effectiveness of rate-control therapy, and moderately incremented treadmill protocols are warranted. The reduction in exercise capacity associated with AF is a direct function of the underlying heart disease In the absence of other clinical indications for stopping, persons with AF may be safely taken to fatigue or shortness of breath endpoints Contraindications to exercise testing in AF are mostly related to comorbidities and other underlying conditions, such as the following: Instability of chronic heart failure Valvular disease Complex ventricular arrhythmias

Atrial Fibrillation Recommendations for Exercise Testing HESS 509 Atrial Fibrillation CHAPTER ELEVEN Recommendations for Exercise Testing Interpretation of the exercise electrocardiogram (ECG) is made more difficult in AF because many individuals with AF take medications to control the rate response and have underlying heart disease. Digoxin helps to control the ventricular response during exercise, but it also has diffuse effects on the ST-segment response, including false-positive (ECG) changes. Other AV nodal suppressants, including calcium channel blockers and β-blockers, can mask ischemic changes, and β-blockers are likely to reduce exercise capacity

HESS 509 Atrial Fibrillation CHAPTER ELEVEN Considerations for Exercise Testing in Atrial Fibrillation Digoxin: may control ventricular response; diffuse ST effects Verapamil: may mask ischemia and decrease heart rate response to exercise Diltiazem, verapamil: help control ventricular response; may improve exercise capacity β-blockers: help control ventricular response; may reduce exercise capacity, particularly with nonselective medications; decrease submaximal and maximal heart rate and blood pressure Bundle branch block: common in people with AF; makes determination of ischemia difficult Left ventricular hypertrophy: common in persons with AF; makes determination of ischemia more difficult Age-predicted maximal heart rate targets: not valid Irregular ventricular response: may make blood pressure determination less precise or more difficult

Atrial Fibrillation Recommendations for Exercise Programming HESS 509 Atrial Fibrillation CHAPTER ELEVEN Recommendations for Exercise Programming Major factors to consider in exercise programming for individuals with AF: Daily variation in ventricular rate In some cases, the intermittent nature (presence or absence) of AF Inherent unreliability of the pulse rate for prescribing exercise intensity Adequacy of anticoagulation in those on anticoagulation therapy Concomitant or underlying heart disease Since AF is frequently accompanied by underlying cardiac disease, exercise programming for these conditions is the major consideration in selecting goals and rate of progression. Atrial fibrillation can have day-to-day variations in ventricular response that can lead to symptoms of low cardiac output (pre-syncope, syncope). This assessment is an important precaution before beginning every exercise session

Atrial Fibrillation Recommendations for Exercise Programming HESS 509 Atrial Fibrillation CHAPTER ELEVEN Recommendations for Exercise Programming Because AF has a variably irregular ventricular response rate, exercise intensity cannot be based on heart or pulse rate but should be prescribed based on work rate and perceived exertion. Frequency, duration, intensity, and progression of exercise are similar to those for individuals in normal sinus rhythm and can follow standard ACSM Guidelines. AF can be intermittent. The rhythm should therefore be determined every day. This influences the patient’s heart rate response to exercise, exercise tolerance, and level of fatigue. It is also important to note that AF has varied effects; some patients experience fatigue while others do not. Finally, many people with AF are elderly, and one must consider comorbid conditions such as osteoporosis, coronary disease, diabetes, and obesity when developing the exercise program.

Atrial Fibrillation Recommendations for Exercise Programming HESS 509 Atrial Fibrillation CHAPTER ELEVEN Recommendations for Exercise Programming Several precautions should be considered during exercise programming: Longer sampling of the pulse may be needed to reliably measure heart rate. Atrial fibrillation has varied effects; some people experience fatigue, while others do not. Atrial fibrillation is frequently intermittent, so ascertain rhythm daily. Many with AF are elderly, so consider comorbid conditions. END