What medications in this regimen, including atorvastatin, lisinopril (Angiotensin-Converting Enzyme Inhibitor), metoprolol (Beta Blocker), are most likely to cause sinus bradycardia in this patient?

From the Guidelines

Metoprolol is the medication most likely causing this patient's sinus bradycardia. Metoprolol is a beta-blocker that works by blocking beta-adrenergic receptors in the heart, which reduces the influence of the sympathetic nervous system. This leads to decreased heart rate, contractility, and blood pressure. Beta-blockers commonly cause bradycardia (heart rate less than 60 beats per minute) as a side effect, and this patient's heart rate is significantly below normal 1.

Key Points to Consider

• While lisinopril (an ACE inhibitor) and atorvastatin (a statin) can have cardiovascular effects, they typically don't cause significant bradycardia.
• The 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay recommends that when sinus bradycardia is the consequence of nonessential medications, withdrawal of the offending drug or dosage reduction can improve the heart rate and symptoms 1.
• Given the patient's history, metoprolol is an appropriate medication, but the dose may need adjustment to address the bradycardia, especially if the patient develops symptoms such as dizziness, fatigue, or syncope.

Management Considerations

• If the patient remains asymptomatic, careful monitoring might be sufficient without dose adjustment.
• However, if symptoms persist or worsen, consideration should be given to adjusting the metoprolol dose or switching to an alternative medication that does not cause bradycardia, as suggested by the guideline 1.

From the FDA Drug Label

Bradycardia, including sinus pause, heart block, and cardiac arrest have occurred with the use of metoprolol. Patients with first-degree atrioventricular block, sinus node dysfunction, or conduction disorders may be at increased risk. Monitor heart rate and rhythm in patients receiving metoprolol. If severe bradycardia develops, reduce or stop metoprolol

• Metoprolol is the medication most likely to cause sinus bradycardia in this patient, as it can slow the sinus rate and decrease AV nodal conduction 2.
• The FDA drug label for metoprolol warns about the risk of bradycardia, including sinus pause and heart block, and recommends monitoring heart rate and rhythm in patients receiving the medication 2.
• Atorvastatin and lisinopril are not directly associated with an increased risk of sinus bradycardia based on the provided drug labels.

From the Research

Medications Causing Sinus Bradycardia

The medications in the regimen that are most likely to cause sinus bradycardia include:

• Metoprolol (Beta Blocker) 3, 4, 5, 6, 7
• The combination of metoprolol and other medications, such as terbinafine, may increase the risk of sinus bradycardia due to drug-drug interactions 4

Risk Factors for Bradycardia

The following factors may increase the risk of bradycardia:

• Female gender 3
• Emergency admission 3
• Dilated cardiomyopathy 3
• Lower left ventricular ejection fraction 3
• Mitral stenosis 3
• Chronic kidney disease 3
• Higher potassium levels 3
• QRS duration > 120 ms 3
• Use of immediate-release metoprolol formulation 7

Comparison of Medications

• Metoprolol and ivabradine have been compared in the treatment of inappropriate sinus tachycardia, with ivabradine being more effective in relieving symptoms during exercise or daily activity 5
• Bucindolol has been shown to have a lower risk of bradycardia compared to metoprolol in patients with atrial fibrillation 6