Heart Rate Target During Exercise in Chronic AFib with HFrEF
For patients with chronic atrial fibrillation and heart failure with reduced ejection fraction (HFrEF), you should adjust pharmacological treatment to keep the heart rate in the physiological range during exercise, which typically means targeting 90-115 beats per minute during moderate exercise activity.
Guideline-Based Approach
The 2014 AHA/ACC/HRS guidelines provide a Class I recommendation that assessment of heart rate control during exercise and adjustment of pharmacological treatment to keep the rate in the physiological range is useful in symptomatic patients during activity 1, 2. This is the cornerstone recommendation for your patient population.
Understanding "Physiological Range"
While the guidelines emphasize keeping heart rate in the "physiological range," older clinical practice recommendations suggested:
- Resting heart rate: 60-80 beats/min
- Moderate exercise: 90-115 beats/min 3
However, real-world data shows these targets are often not achieved. In a study of 1,097 consecutive AF patients referred for exercise testing, median heart rate at moderate exercise was 128 beats/min—higher than guideline recommendations 3.
Practical Considerations for HFrEF Patients
Key caveat: Patients with HFrEF and AF demonstrate different exercise physiology compared to those in sinus rhythm:
- They have higher heart rates at low levels of exercise but attenuated maximal heart rate responses 4
- Excessive heart rate responses to minor exercise may have deleterious effects on left ventricular function 4
- Exercise performance is reduced with lower peak VO2 compared to sinus rhythm patients 5
Medication Strategy
Beta blockers are your first-line agent for rate control during exercise in HFrEF patients with AF 1, 2. The guidelines recommend:
- Class IIa: A combination of digoxin and a beta blocker is reasonable to control both resting and exercise heart rate 1, 2
- Digoxin alone is effective for resting heart rate control but insufficient for exercise rate control 6
- Beta blockers were significantly more effective at achieving heart rate control during exercise compared to other agents 3
Monitoring Approach
You must assess heart rate control during actual exercise or activity, not just at rest 1, 2. This means:
- Perform exercise testing or assess heart rate during activities of daily living
- Titrate medications based on exercise response, not just resting heart rate
- Recognize that resting heart rate control does not predict adequate exercise rate control
Common Pitfall
Do not rely on resting heart rate alone. Many patients have acceptable resting heart rates but develop excessive tachycardia with minimal exertion, which can worsen heart failure symptoms and functional capacity 4. The guideline specifically emphasizes assessment during activity for symptomatic patients 1, 2.
When Medical Therapy Fails
If pharmacological rate control is insufficient or not tolerated, AV node ablation with ventricular pacing (or preferably cardiac resynchronization therapy in HFrEF) is reasonable 1, 2. However, this should only be considered after attempting medical therapy—performing AV node ablation without a pharmacological trial is contraindicated (Class III: Harm) 1, 2.