A 47-year-old man is brought to the emergency department by his wife due to a 2-day history of lightheadedness and generalized weakness. The patient nearly lost consciousness on 2 occasions and has been unable to get out of bed since this morning. He has no chest pain, headaches, or nausea. Other medical problems include chronic low back pain, type 2 diabetes mellitus with evidence of retinopathy and proteinuria, and hypertension for which he was recently started on losartan. His other medications include ibuprofen, amitriptyline, and low-dose aspirin.
On examination, he appears lethargic with mild muscle weakness in both lower extremities. Initial blood pressure is 105/80 mm Hg.
His rhythm strip is shown here.
Which of the following is the most likely cause of this patient's symptoms?

Question

A 47-year-old man is brought to the emergency department by his wife due to a 2-day history of lightheadedness and generalized weakness.  The patient nearly lost consciousness on 2 occasions and has been unable to get out of bed since this morning.  He has no chest pain, headaches, or nausea.  Other medical problems include chronic low back pain, type 2 diabetes mellitus with evidence of retinopathy and proteinuria, and hypertension for which he was recently started on losartan.  His other medications include ibuprofen, amitriptyline, and low-dose aspirin.
On examination, he appears lethargic with mild muscle weakness in both lower extremities.  Initial blood pressure is 105/80 mm Hg.
His rhythm strip is shown here.
Which of the following is the most likely cause of this patient's symptoms?

Quizplus · Accepted Answer

11ec193a_95b7_547a_853d_ed3f0b58d188_MD0002_00 This patient's ECG shows complete absence of P wave activity (atrial asystole) and QRS widening due to intraventricular conduction delay. This is most likely due to hyperkalemia in the setting of worsening renal failure after starting losartan therapy (angiotensin receptor blocker). The earliest ECG manifestations of hyperkalemia include tall and peaked T waves with a shortened QT interval, and more dramatic changes can occur as the condition worsens. Clinical manifestations of severe hyperkalemia include muscle weakness/paralysis and cardiac conduction abnormalities and arrhythmias. These typically occur with serum potassium concentrations >7 mEq/L. Management of patients with hyperkalemia and ECG changes includes intravenous calcium to reduce cardiotoxicity, along with insulin and glucose, sodium bicarbonate, and/or β2 agonists to lower serum potassium concentration. Management (Choice A) Tricyclic antidepressant overdose usually presents with anticholinergic excess (ie, confusion, tachycardia, fever, urinary retention, and blurred vision) and is associated with PR, QRS, and QT prolongation as well as ventricular arrhythmias. (Choice C) Ischemic strokes typically present with focal weakness and are usually not associated with significant ECG changes unless there is concurrent cardiac ischemia. (Choice D) Myocardial ischemia should always be a concern in a diabetic patient, but the ST segment changes in this patient are likely due to the widened QRS. In addition, ischemia can cause atrioventricular block, but does not usually cause absent P waves, as seen in this case. (Choice E) Sick sinus syndrome (SSS) encompasses a variety of situations in which the sinus node is dysfunctional (eg, sinus arrest). Although this tracing may represent sinus arrest with a very slow and wide escape rhythm of ventricular origin, SSS is a diagnosis of exclusion after investigation of all other reversible causes (ie, electrolytes, drug toxicity, and ischemia). Educational objective: Tall, peaked T waves with shortened QT interval are the earliest ECG manifestations of hyperkalemia. PR interval prolongation, atrial asystole, and QRS widening with progression to sine wave pattern occur with worsening hyperkalemia. Treatment involves acute drug therapy (eg, calcium, insulin, glucose) or hemodialysis in more severe cases. __________ References: Electrocardiographic manifestations of hyperkalemia. (http://www.ncbi.nlm.nih.gov/pubmed/11043630)

A 47-Year-Old Man Is Brought to the Emergency Department by His