An unusual case of cardiac glycoside toxicity

Abstract

Cardiac glycosides are naturally occurring toxins that reversiblyinhibit the sodium–potassium adenosine triphosphatase (Na–K–ATPase) exchanger in myocardial cells. They are found in various plantspecies, such as foxglove (Digitalis purpurea, Digitalis lanata), ouabain(Strophanthus gratus), common oleander (Nerium oleander), yellowoleander (Thevetia peruviana), and sea mango (Cerbera manghas) [1].Self-poisoningwith the seeds or fruits of theseplantsisa major clinicalprobleminpartsofthedevelopingworldcausingasignificantnumberofdeaths each year [2]. In particular though, the seeds from the Cerberaodollamtree (also known asthe“Suicide tree” or “Pong-pongtree”)areexcessively toxic, containing cerberin as the main active cardiacglycoside, and often used for suicide or homicide in certain rural areasof South Asia [3]. In countries far from the natural habitat of theseextremely toxic plants, poisonings are relatively unknown to Westernphysicians and rarely reported. We present an unusual case of acutecardiacglycosidetoxicityduetosuicidalingestionof“Pong-pong”seedspurchased from an online website.A 51-year-old womanwith a history of depression and prior suicideattempts with various drug overdoses presented to the EmergencyDepartment complaining of nausea, vomiting, diarrhea, and chesttightness since awakening that morning. On physical examination,she was lethargic and profoundly bradycardic with an irregular pulse.Her heart rate was 30 beats per minute (bpm) and blood pressure90/60 mm Hg. An electrocardiogram (ECG) demonstrated atrialflutter(AFl) with variable atrioventricular (AV) block and slowventricular response, diffuse ST-segment depressions, shortened QTinterval, and peaked T-waves (Fig. 1A). Laboratory studies weresignificant for a serum potassium level of 7.5 mmol/L (normal: 3.5 –5.1),calcium of 10.9 mg/dL (normal 8.6 –10.2), and creatinine of 2.6 mg/dL(normal:0.7–1.2).CardiacenzymesweremildlyelevatedwithatroponinT level of 0.07 ng/mL (normal: b0.03). Comprehensive serum and urinetoxicologyscreenswereunremarkable.Adigoxinconcentrationlevelwasundetectable (b0.3 ng/mL).The patient was administered atropine for her symptomaticbradycardia, which improved with a heart rate of 91 bpm. Calciumgluconate, sodium bicarbonate, glucose, and insulin therapy weregiven for severe hyperkalemia in the setting of an acute kidney injury.A repeat ECG showed continuedAFlwithvariable AV block, shortenedQT interval, and deeper, downsloping ST-segment depressions(Fig.1B). A repeat serum potassium level was 5.5 mmol/L, correlatingwithresolutionofthepeakedT-wavesonECG.Arepeatserumcalciumlevel was 10.3 mg/dL, though the QT interval remained shortened onECG. She was transferred to the Intensive Care Unit (ICU) forcontinued supportive therapy.Upon further questioning in the ICU, the patient admitted to theintentionalingestionofanunknownquantityofseedsobtainedfroma“Pong-pong” tree she purchased several weeks prior from an onlinewebsite. The Poison Control Center was immediately called, and thepatientsubsequentlyreceived10vialsofempiricdigoxinimmuneFab.The following ECG revealed a return to normal sinus rhythm,continued QT interval shortening, and persistent ST-segment depres-sions with biphasic T waves, though improved compared to the priorECGwithresolutionofdysrhythmias(Fig.1C).Furtherevaluationwithan echocardiogram and cardiac catheterization was normal. She wasadministered another 10 vials of digoxin immune Fab with ultimatenormalization of the QT interval and resolution of ST-segmentdepressions within 24 h (Fig.1D). The patient recovered uneventfullyand later discharged in stable condition.To the best of our knowledge, this is the first reported case in themedical literature of Cerbera odollam poisoning in the United States.Although common in certain parts of South Asia, non-pharmacologiccardiac glycoside toxicity is rare in the United States. Of more than2.3 million human exposures reported in the 2011 National PoisonData System, only 569 calls were received for plant cardiac glycosides(excluding drugs) [4].