ECG Challenge

For Lethargic Patient, Trouble Is Brewing

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A 72-year-old man presents with a primary complaint of lethargy. He emigrated from Southeast Asia to the United States about a year ago and neither speaks nor understands English. His grandson, who is fluent, accompanies him to his appointment. Through his grandson, the patient explains that he has become increasingly tired in the past four months—to the extent that exercise and activities of daily living have become difficult. The patient’s libido also has been affected. In an effort to correct this, he visited a local Asian goods store, where he was given a mixture of herbs from which to brew tea to treat his symptoms. For three weeks, he consumed the tea twice daily. Initially, his energy, stamina, and libido improved. However, his symptoms eventually returned, so he doubled his tea consumption with the idea that this would improve his condition. Unfortunately, in addition to his lethargy, he is now experiencing palpitations, a fluttering sensation in his chest, and occasional dizziness. He denies chest pain, shortness of breath, nocturnal dyspnea, syncope, or near syncope. Medical history is difficult to elicit. He denies prior history of hypertension, myocardial infarction, congestive heart failure, or diabetes. Neither he nor his grandson understands the concept of arrhythmias (eg, atrial fibrillation). He was treated for tuberculosis as a child and has had no recurrence. He has had no surgeries. The patient takes no prescribed medications. He does, however, use herbal products including ginseng, horny goat weed, and fenugreek (in addition to his herbal tea). He has no known drug allergies. Social history reveals that the patient lives with his son’s family, having moved to the US from Thailand after his wife died of old age. He worked as a farmer his entire life. He drinks one ounce of whiskey daily and smokes 1 to 1.5 packs of cigarettes a day. The review of systems is noncontributory. His grandson is reluctant to ask the patient many questions regarding his health, once he notices his grandfather’s agitation at answering questions. The physical exam reveals a thin, elderly male with weathered skin who is in no acute distress. Vital signs include a blood pressure of 118/62 mm Hg; pulse, 80 beats/min and regular; respiratory rate, 16 breaths/min; and temperature, 97.8°F. His height is 62 in and his weight, 117 lb. The HEENT exam is remarkable for arcus senilis and multiple missing teeth. There is no jugular distention, and the thyroid is not enlarged. The lungs reveal coarse breath sounds that clear with coughing in all lung fields. (The patient has an occasional harsh cough.) The cardiac exam is positive for a grade II/VI systolic murmur best heard at the left upper sternal border, which radiates to the carotid arteries. The rhythm is regular at a rate of 80 beats/min, and there are no clicks or rubs. The abdomen is scaphoid, soft, and nontender, with no palpable masses. The peripheral pulses are strong and equal bilaterally. Extremities demonstrate full range of motion, and the neurologic exam is grossly intact. Routine laboratory tests including a complete blood count and electrolyte panel are obtained. Because you are unsure of his medication regimen, you order a toxicology screen. You are surprised to see a serum digoxin level of 0.7 ng/mL. Finally, given the patient’s symptoms of palpitations and dizziness, you order an ECG. It shows the following: a ventricular rate of 87 beats/min; PR interval, 218 ms; QRS duration, 130 ms; QT/QTc interval, 416/500 ms; P axis, 24°; R axis, 49°; and T axis, 45°. What is your interpretation of this ECG?


 

ANSWER

The correct interpretation is an atrial tachycardia with 2:1 ventricular conduction. The ventricular rate is 87 beats/min (690 ms), and the atrial rate is 174 beats/min (345 ms). Two P waves are present for each QRS, which excludes a first-degree atrioventricular block. The less obvious P wave is found in the terminal portion of the QRS complex. (You may convince yourself of this by using calipers to measure the R-R interval, dividing that measurement in half, and then applying it to the ECG. You will see the P waves march through without changing the ventricular response.)

A nonspecific intraventricular conduction delay is also present. The QRS duration is > 100 ms; however, the criteria for right or left bundle branch block are absent.

A thorough investigation revealed that the clerk formulating the herbs for the tea was using, among other things, dried foxglove. Foxglove has been used as a remedy for lethargy in the elderly, presumably because it inadvertently treats symptoms of congestive heart failure. It was the tea consumption that accounted for the presence of digoxin in the patient’s blood. (Recall that there is a substantial overlap between therapeutic and toxic serum concentrations of digoxin.) When the patient stopped consuming the tea, his atrial tachycardia resolved, as did his symptoms.

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