WBR1089

Author	[[PageAuthor::Mohamed Moubarak, M.D. [1]]]
Exam Type	ExamType::USMLE Step 3
Main Category	MainCategory::Primary Care Office
Sub Category	SubCategory::Cardiovascular, SubCategory::Electrolytes
Prompt	[[Prompt::A 57-year-old male comes to your office for follow up. He is a newly diagnosed lung cancer patient, and undergoes his first round of cisplatin. He has insignificant past medical history. On examination, his BP is 100/80 mmHg, irregular heart rate 50 beat per minute, temperature 37 C (98.6 F), respiratory rate is 17/minute. His laboratory tests are: Sodium 135 Potassium 6.8 Chloride 108 CO2 20 BUN 35 Creatinine 3.4 Glucose 152 Calcium 7.5 What would be the most likely finding on this patient’s EKG?]]
Answer A	AnswerA::Shortened P-R segment
Answer A Explanation	[[AnswerAExp::Incorrect Hyperkalemia does not cause shortened P-R segment. The most common causes of shortened P-R segment include AV junctional rhythm, and Wolff-Parkinson-White syndrome.]]
Answer B	AnswerB::Abnormally prominent U waves
Answer B Explanation	[[AnswerBExp::Incorrect Abnormally prominent U waves are characteristically seen in severe hypokalaemia. U waves are prominent if > 1-2mm or 25% of the height of the T wave. The most common cause of prominent U waves is bradycardia.]]
Answer C	AnswerC::Widened QRS complexes
Answer C Explanation	[[AnswerCExp::Correct Hyperkalemia will produce significant EKG abnormalities, including peaked T waves and widened QRS complexes]]
Answer D	AnswerD::Flattened T waves
Answer D Explanation	[[AnswerDExp::Incorrect Flattened T waves may indicate myocardial ischemia, or hypokalemia.]]
Answer E	AnswerE::Atrial fibrillation
Answer E Explanation	[[AnswerEExp::Incorrect Hyperkalemia will produce significant EKG abnormalities, including peaked T waves and widened QRS complexes. Bradycardia and irregular heart rate on physical examination are suggestive of the cardiac effects of hyperkalemia.]]
Right Answer	RightAnswer::C
Explanation	[[Explanation::The patient has tumor lysis syndrome. The destruction of malignant cells by chemotherapeutic agents will lead to the release of intracellular contents, including potassium, phosphorus, and uric acid (from nucleic acids). This can result in hyperkalemia, hyperuricemia, and hyperphosphatemia. Hyperkalemia will produce significant EKG abnormalities, including peaked T waves and widened QRS complexes. The presence of bradycardia and irregular heart rate on physical examination are suggestive of the cardiac effects of hyperkalemia, which can lead to life threatening arrhythmias if not managed properly. Educational Objective: Hyperkalemia due to tumor lysis syndrome will produce significant EKG abnormalities, including peaked T waves and widened QRS complexes. References: http://www.wikidoc.org/index.php/Tumor_lysis_syndrome]]
Approved	Approved::No
Keyword	[[WBRKeyword::Tumor lysis syndrome]]
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::