Anticholinergic Avoids Pacemaker in Case of AF With Bradycardia

Fran Lowry

June 06, 2018

Hyoscyamine, an anticholinergic drug, may allow some patients who would otherwise require a pacemaker for slow ventricular response during atrial fibrillation (AF)  to avoid it, a case report suggests.  

"To our knowledge, this is the first report of hyoscyamine or any other anticholinergic drug being used to avoid pacemaker placement in a patient with symptoms caused by a slow ventricular response during atrial fibrillation," write Scott A. Helgeson, MD, and colleagues from Mayo Clinic, Jacksonville, Florida.

Additional studies are needed to see whether this patient's successful outcome can be replicated in others, they caution.

Still, clinicians may want to attempt this approach in patients with AF who have a slow ventricular response and would qualify for a pacemaker but whose comorbidities make such an intervention problematic, the authors suggest.

"We advise administering a test dose of 0.1 intravenous glycopyrrolate in these patients, because this agent has a relatively short half-life," they conclude. The heart rate should increase at least 20% within 10 minutes of administration, they note.

"If the test is successful, we recommend sublingual hyoscyamine, 0.125 mg 4 times daily, for longer-term treatment and believe that this dose can be increased to 1.5 mg/dif needed."

The report was published online May 15 in Annals of Internal Medicine.

AF typically presents with tachycardia, but "atrial fibrillation with bradycardia is much less common," the researchers note. "Bradycardia may be due to increased vagal tone, drugs affecting the atrioventricular node, or conduction system disease. Symptomatic bradycardia caused by conduction system disease is often treated with a pacemaker, because medications are not usually effective in this condition," they write.

Anticholinergic drugs, such as atropine, glycopyrrolate, and hyoscyamine, which inhibit receptors in smooth and cardiac muscle, are often used to inhibit gastrointestinal propulsion and decrease urinary bladder contractions and secretions of the pharynx, stomach, trachea, and bronchus. They are also used preoperatively to block cardiac vagal inhibitory reflexes during intubation and anesthesia induction, they write.

In this report, the authors describe the case of a 98-year-old man with several comorbidities, including a long-term in-dwelling catheter, dementia, AF, and metastatic prostate cancer, who presented to the emergency department with recurrent syncope and bradycardia.

The patient was a poor candidate for a pacemaker because of his dementia, which prevented him from following the activity restrictions required after pacemaker placement to avoid lead dislodgement; he also used a walker, which involves upper-extremity weight bearing and could have strained the ipsilateral pectoralis major, thereby increasing the risk for lead dislodgement. In addition, his urinary catheter would prevent him from experiencing urinary retention, which is a common adverse effect of hyoscyamine in such patients, the authors note.

The patient was already receiving amlodipine, dabigatran, and enzalutamide. His blood pressure was 72/40 mm Hg, heart rate was 35 beats per minute, and electrocardiography showed AF with a slow ventricular response and right bundle-branch block.

After 0.5 mg of intravenous atropine was administered, the patient's heart rate increased to 50 beats per minute and blood pressure increased to 118/73 mm Hg.

The patient also had an irregularly irregular heart rhythm but no murmurs, jugular venous distention, or edema. He remained in AF overnight with a heart rate between 40 and 50 beats per minute.

The researchers considered placing a leadless pacemaker but opted instead to treat the patient first with medication because of his comorbidities.

They administered intravenous glycopyrrolate, 0.1 mg, and the patient's heart rate increased substantially for 30 minutes. They then administered 0.125 mg of sublingual, immediate-release hyoscyamine and observed a similar but more prolonged response.

The patient was discharged the next day with a resting heart rate between 70 and 80 beats per minute, and he received the same type and dose of hyoscyamine four times daily.

The patient returned 4 weeks later for routine follow-up. He had not experienced any syncope, and a repeat electrocardiogram showed a resting heart rate of 73 beats per minute.

"Intriguing" Case Report

"It's just a case report, and so there's not that much to say," said Kenneth A. Ellenbogen, Kimmerling Professor of Cardiology and chair, Division of Cardiology, VCU Pauley Heart Center, Medical College of Virginia, Richmond, commenting for theheart.org | Medscape Cardiology.

"Those types of drugs that have effects on the autonomic nervous system are not particularly potent. I think we're far away from being able to roll these drugs out as treatment for arrhythmias or treatment to manipulate the heart rate," Ellenbogen said.

"The thought was that these drugs may slow the heart rate, but they just haven't been all that useful," he added. "They may be used transiently, in a pinch, and this is certainly an intriguing single case report, but I think we've got a long way to go before something like this could actually be implemented on a wider scale in clinical practice."  

The authors and Ellenbogen have disclosed no relevant financial relationships.

Ann Intern Med. Published online May 15, 2018. Abstract

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