Severe Bradycardia: Patient Outfoxed by Lady's Glove

Abstract

We report the case of a 66-year-old woman who presented to the emergency department with vigorous, frequent vomiting and lethargy. Her symptoms had started after the ingestion of a drink made of herbs from a friend's garden. She had consumed similar drinks before, but this time it tasted “more bitter than usual.” On admission, the patient's abdomen was tender with slight pain and active bowel movements. Neurologic deficits were absent. The electrocardiogram showed pronounced bradyarrhythmia (Figure 1) with down-slope ST-segment depression. Electrolytes were within normal range (K+ 4.2 mmol/L). The patient did not take any regular medication. Although standard toxicologic screening was negative, testing for digoxin showed a supratherapeutic level of 5.1 nmol/L (therapeutic range, 1.3-2.6 nmol/L) 16 hours after ingestion of the herbs. Antidotal therapy was instantly initiated with 120 mg anti-digoxin Fab-fragments (DigiFab, Protherics Inc., Nashville, Tenn) administered intravenously along with substitution of potassium administered intravenously. Over several hours, the heart rate normalized and lethargy improved. Electrocardiogram alterations gradually changed (Figure 1). A botanist identified foxglove or Lady's Glove (Digitalis purpurea) close to numerous borage plants (Borago officinalis) in the friend's garden. Because the plants were not in bloom, the patient had mistaken their similar leaves for borage (Figure 2). Seeing the foxglove plant, she remembered having regularly used 1 to 2 leaves of it for her herbal drinks. Retrospectively, she reported recurrent transient palpitations during the last few months. The day before admission she had consumed a larger amount of Digitalis purpurea leaves. This resulted in a life-threatening acute on chronic intoxication. Cardiac glycosides have played an important role in the therapy of congestive heart failure since Sir William Withering described the use of Digitalis purpurea in 1785. Cardiac glycosides all contain a steroid nucleus with an unsaturated lactone ring (C17) and at least 1 glycosidic residue (C3). They reversibly inhibit the Na+-K+-ATPase membrane pump, resulting in an increase in intracellular calcium concentration in the myocyte, which augments inotropy. They also increase vagal tone and slow the rate of the sinoatrial node and conduction through the atrioventricular node. The toxic arrhythmogenic effects of these substances are due to a combination of direct effects on the myocardium and neurally mediated increases in autonomic activity.1Hauptman P.J. Kelly R.A. Digitalis.Circulation. 1999; 99: 1265-1270Crossref PubMed Scopus (244) Google Scholar The clinical features of digitalis poisoning are well described and include gastrointestinal, cardiac (especially arrhythmias), and neurologic symptoms. The treatment of severe digitalis intoxication was revolutionized in 1976 by the introduction of digoxin-specific antibody (Fab) fragments, which are highly effective and safe, and have resulted in improved survival.1Hauptman P.J. Kelly R.A. Digitalis.Circulation. 1999; 99: 1265-1270Crossref PubMed Scopus (244) Google Scholar Unfortunately, the high cost of this treatment is a significant problem in developing countries.2Roberts D.M. Buckley N.A. Antidotes for acute cardenolide (cardiac glycoside) poisoning.Cochrane Database Syst Rev. 2006; (CD005490)Google Scholar One to 2 leaves of the digitalis plant are estimated to be potentially fatal for an adult. All parts of the plant contain different potent cardiac glycosides. Thus, the serum digoxin concentration does not necessarily correspond to the severity of symptoms in acute poisoning. Moreover, an elevated serum digoxin level is not specific for Digitalis purpurea poisoning, because other plants also contain cardioactive steroids, for example, Oleander (Nerium oleander), Lily of the Valley (Convallaria majalis), and False Hellebore (Adonis vernalis). Glycoside intoxication should always be considered in patients with typical symptoms even if no medication with cardiac glycosides is reported. In this rare case of an acute on chronic intoxication with herbal cardioactive glycosides from Digitalis purpurea, prompt treatment with anti-digoxin Fab fragments and potassium was effective and safe.