WBR0461

Author	[[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pathology
Sub Category	SubCategory::Cardiology
Prompt	[[Prompt::A 62-year-old man is transferred by EMS for severe chest pain and dyspnea at rest for the past 30 minutes. The patient has a medical history significant for hyperlipidemia, uncontrolled diabetes mellitus, and hypertension. He smokes 2 packs of cigarettes each day for the past 40 years. Prior to arrival to the hospital, ECG in the EMS shows ST-segment-elevation more than 2 consecutive leads. The patient is diagnosed with ST-segment-elevation myocardial infarction (STEMI). Despite appropriate and timely management, the patient dies prior to hospitalization. Which of the following is this patient's most likely cause of death?]]
Answer A	AnswerA::Arrhythmia
Answer A Explanation	[[AnswerAExp::Fatal ventricular arrhythmia is the most common cause of death in the first few hours following MI.]]
Answer B	AnswerB::Ventricular rupture
Answer B Explanation	[[AnswerBExp::A ventricular rupture is a potentially fatal complication of MI, typically occurring within the subsequent 6-10 days post-MI. The severely injured ventricular wall may result in rupture, which occurs during the inflammatory response induced by the infarction process.]]
Answer C	AnswerC::Dressler syndrome
Answer C Explanation	[[AnswerCExp::Dressler syndrome is a rare autoimmune fibrinous pericarditis that occurs several weeks following MI.]]
Answer D	AnswerD::Cardiac tamponade
Answer D Explanation	[[AnswerDExp::Cardiac tamponade results in an overall cardiovascular collapse due to severe hypotension. Cardiac tamponade stems from a pericardial effusion, which restricts the normal expansion of the ventricles and leads to the normalization of pressures in all cardiac chambers. Cardiac tamponade does not typically occur acutely following MI. Cardiac tamponade usually occurs with ventricular free wall rupture that causes rapid fluid accumulation within the pericardium and cardiac tamponade.]]
Answer E	AnswerE::Endocarditis
Answer E Explanation	[[AnswerEExp::Endocarditis is not a common complication of MI.]]
Right Answer	RightAnswer::A
Explanation	[[Explanation::More than 80% of myocardial infarctions (MI) are caused by thrombus formation in the coronary arteries. Thrombosis causes ischemia to myocytes with insufficient myocardial perfusion within seconds. The acute phase following an MI is a critical period marked by high rates of cardiovascular complications and mortality. The risk of arrhythmia significantly increases following MI. Fatal ventricular arrythmias are considered the most common cause of post-MI mortality and the leading cause of death prior to hospitalization. Arrhythmias are thought to be caused by either the increased automaticity due to shortening of the action potential and refractory period in the membranes of ischemic cells or reperfusion injury caused by free oxygen species. The location of an MI is associated with the risk of arrhythmia. While anterior MI is associated with atrial fibrillation, atrial flutter, paroxysmal atrial tachycardia, and accelerated AV junctional rhythm (Anterior MI is associated with a sympathetic surge), posterior and inferior MI is associated with bradycardia and junctional escape rhythms (Posterior MI is associated with excessive vagal response because RCA usually supplies the posterior portion of the heart and the SA node). Although acute arrhythmias are significant complications post-MI, several other electrical and mechanical complications may also occur in the non-acute MI phase. Common complications post-MI include: Heart failure Cardiogenic shock Ventricular free wall rupture that may lead to cardiac tamponade Interventricular septum rupture that may cause septal defects (eg. VSD) Papillary muscle rupture and mitral regurgitation Ventricular pseudoaneurysm and aneurysm formation Fibrinous pericarditis Dressler syndrome Educational Objective: The risk of arrhythmia significantly increases following MI. Fatal ventricular arrythmias are considered the most common cause of post-MI mortality and the leading cause of death prior to hospitalization. References: O'Donnell L. Complications of MI: beyond the acute stage. Am J Nurs. 1996;96(9):25-30. First Aid 2014 page 290]]
Approved	Approved::Yes
Keyword	WBRKeyword::Chest pain, WBRKeyword::Ventricular arrhythmia, WBRKeyword::Fibrillation, WBRKeyword::Cardiac arrest, WBRKeyword::MI, WBRKeyword::Myocardial infraction, WBRKeyword::STEMI, WBRKeyword::Arrhythmia, WBRKeyword::Death
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::