View source for WBR0839

 {{WBRQuestion
|QuestionAuthor=Neeraja Danda M.B.B.S
|ExamType=USMLE Step 2 CK
|MainCategory=Internal medicine
|SubCategory=Cardiovascular
|MainCategory=Internal medicine
|SubCategory=Cardiovascular
|MainCategory=Internal medicine
|SubCategory=Cardiovascular
|MainCategory=Internal medicine
|MainCategory=Internal medicine
|SubCategory=Cardiovascular
|MainCategory=Internal medicine
|SubCategory=Cardiovascular
|MainCategory=Internal medicine
|SubCategory=Cardiovascular
|MainCategory=Internal medicine
|SubCategory=Cardiovascular
|MainCategory=Internal medicine
|MainCategory=Internal medicine
|SubCategory=Cardiovascular
|Prompt=A 38 Year old male crashed his car in to a tree while speeding. Vitals are Pulse rate 115/min, Blood pressure 100/70 and become 78/58 on inhalation and respiratory rate 28/min. On physical examination neck veins are distended. Electrocardiogram shows QRS complexes of varying heights. Such presentation on Electrocardiogram is characteristic of which of the following?
|Explanation=The patient in this vignette is suffering from pericardial tamponade. Electical alternans is defined by an electrocardiogram with QRS complexes of varying heights, a common feature of pericardial tamponade. Tachycardia, hypotension, pulsus paradoxus and jugular venous distension in this case are also characteristic of pericardial tamponade.  In this case, a stab wound has caused ventricular rupture and rapid collection of blood in the pericardium.  As little as 100mL of fluid can cause tamponade in the case of rapid accumulation, such as trauma or ventricular rupture. Pulsus paradoxus is a drop in the blood pressure more than 10 mm of hg on inspiration. Pericardial tamponade is also referred to as cardiac tamponade. 

'''Educational Objective:''' Electrical alternans is characterized by varying heights of QRS complexes on electrocardiogram and is a characteristic finding in pericardial tamponade.

'''References:''' page 64, 99,100, 384 Master the boards step 2 CK second edition, Page 69 Master the boards Step 3 2009

|AnswerA=Constrictive pericarditis
	

|AnswerAExp='''Incorrect''' Electrocardiogram in pericarditis is characterized by ST segment elevation in all the leads.
|AnswerB=Pericardial tamponade
|AnswerBExp=Electical alternans is defined by an electrocardiogram with QRS complexes of varying heights, a common feature of pericardial tamponade.  
|AnswerC=Pneumothorax
|AnswerCExp='''Incorrect''' Pneumothorax is presence of air in the pleural space. It is characterized by decreased breath sounds on the affected side. Electrical alternans is not seen in this condition. However suspicion for pneumothorax following a stab wound to the chest should be high.
|AnswerD=Ischemic heart disease
|AnswerDExp='''Incorrect''' In ischemic heart disease, the electrocardiogram shows ST elevation or depression.  The location of ST segment changes in particular leads can help determine the infracted portion of the heart. 
|AnswerE=Heart failure
|AnswerEExp='''Incorrect''' Heart failure is not characterized by electrical alternans.
|RightAnswer=B
|WBRKeyword=Elactrical Alternans, Pericardial Tamponade
|Approved=Yes
}}