Is it safe to increase the dose of atenolol (beta blocker) in a patient with atrial fibrillation (AFib) and bradycardia (heart rate as low as 39-42 beats per minute) during sleep?

From the Guidelines

It is not safe to take more atenolol if your heart rate is already dropping to 39-42 beats per minute during sleep. In fact, this low heart rate (bradycardia) is concerning and should be discussed with your doctor before continuing your current dose of atenolol. Atenolol is a beta-blocker that intentionally lowers heart rate, but rates below 50 beats per minute can be dangerous for most people. Given your already low nighttime heart rate, increasing your atenolol dose could potentially cause severe bradycardia, which may lead to dizziness, fainting, or more serious complications. You should contact your cardiologist immediately to report these low heart rates and discuss whether your atenolol dose should be adjusted or possibly reduced. Your doctor might consider alternative medications for managing your atrial fibrillation that won't further lower your heart rate. They may also want to evaluate whether you need a pacemaker if the bradycardia is severe or symptomatic. According to the 2016 ESC guidelines for the management of atrial fibrillation 1, beta-blockers such as atenolol are used for rate control therapy, but the guidelines also emphasize the importance of monitoring for side effects, including bradycardia. The guidelines recommend a dose of 25–100 mg once daily for atenolol, but they do not provide specific guidance on what to do if the patient's heart rate is already low. However, the guidelines do suggest that beta-blockers can be useful for symptomatic and functional improvement in patients with atrial fibrillation, despite the lack of prognostic benefit in heart failure with reduced ejection fraction (HFrEF) 1. Continue taking your current medications as prescribed until you speak with your doctor, but do not increase your atenolol dose on your own. Some key points to consider when discussing your treatment with your doctor include:

• The potential risks and benefits of continuing atenolol at your current dose
• The possibility of adjusting your dose or switching to a different medication
• The need for close monitoring of your heart rate and other symptoms
• The potential for alternative treatments, such as a pacemaker, if your bradycardia is severe or symptomatic.

From the Research

Atenolol Dosage and Safety

The patient is concerned about taking more atenolol, given that their heart rate goes as low as 39-42 beats per minute during sleep.

• The initial dosage of atenolol prescribed is 25 mg daily for rate control 2.
• Studies have shown that atenolol can reduce resting heart rate by approximately 25 to 30 beats per minute, although this effect may vary depending on the individual and the presence of other medical conditions 2, 3.
• It is essential to monitor the patient's heart rate and adjust the dosage as needed to avoid excessive bradycardia.

Potential Interactions and Side Effects

• Atenolol may interact with other medications, such as digoxin, and can produce a profound fall in cardiac output in patients with cardiac failure 2.
• Common side effects of atenolol include nausea, headaches, and tiredness, but overall, it is well-tolerated by most patients 2, 3.
• The patient's symptoms, such as a viral illness or respiratory issues, may be contributing to the onset of atrial fibrillation and elevated heart rate, and it is crucial to address these underlying conditions 2.

Thyroid Function and Atenolol

• Atenolol may have effects on thyroid hormone metabolism, although the clinical significance of these effects is not established 2, 4, 5.
• Studies have shown that atenolol can decrease serum T3 levels in hyperthyroid patients, but the mechanism of this effect is not fully understood 4, 5.
• Thyroid function tests may be necessary to determine if the patient's thyroiditis is related to their symptoms and to adjust the treatment plan accordingly 2.