Transient Complete Atrioventricular Block Associated With Herbal Supplement Use

Increasing and easy availability of so-called natural/herbal supplements pose the unique challenge of identifying associated side effects, including arrhythmias in otherwise-healthy individuals.

A 25-year-old female patient presented to the emergency department with fatigue and lightheadedness. The electrocardiogram showed complete AV block with a junctional escape rhythm at 55 beats per minute with QT prolongation (542ms). One week ago, she started to use a herbal medication (Muscle Eze Advanced) for muscle cramps after workouts. Extensive cardiac testing, including complete blood count, complete metabolic panel, TSH, transthoracic echocardiography, urine drug analysis, Lyme antibody were negative. Normal sinus rhythm was restored spontaneously within 1 day of discontinuing the herbal medication. PR and corrected QT intervals returned to baseline over the next two weeks.

Muscle Eze Advanced consists of seven ingredients, including Melissa officinalis and Valeriana officinalis that have negative chronotropic, negative dromotrophic and QT prolonging effects. Recognizing the association between certain over-the-counter supplements and brady-arrhythmias may circumvent need for permanent pacemakers - an important consideration especially in the young.