STEPUP Cardiovascular System: Ischemic Heart Disease - Myocardial Infarction

Question 1

What is MI? What is it most commonly due to? What is the mortality rate and when do deaths occur in relation to hospitalization? What is associated with MI?

Answer 1

1) Necrosis of myocardium as a result of interruption of blood supply (after a thrombotic occlusion of a coronary artery previously narrowed by atherosclerosis)
2) Most cases are due to acute coronary thrombosis: Atheromatous plaque ruptures into the vessel lumen, and thrombus forms on top of this lesion, which causes occlusion of the vessel
3) MI is associated with a 30% mortality rate; half of the deaths are prehospital
4) Most patients with MI have a history of angina, risk factors for CAD, or history of arrhythmias

Question 2

Describe the chest pain associated with MI. Where does it radiate? How does it differ from angina pectoris? What other type of discomfort can patients with MI have?

Answer 2

1) Intense substernal pressure sensation; often described as “crushing” and “an elephant standing on my chest”
2) Radiation to neck, jaw, arms, or back, commonly to the left side
3) Similar to angina pectoris in character and distribution but much more severe and lasts longer. Unlike in angina, pain typically does not respond to nitroglycerin
4) Some patients may have epigastric discomfort

Question 3

What fraction of patients may have asymptomatic MI? What type of patients does asymptomatic MI usually present in?

Answer 3

1) Can be asymptomatic in up to one-third of patients
2) Painless infarcts or atypical presentations more likely in postoperative patients, the elderly, diabetic patients, and women

Question 4

What are some symptoms other than chest pain or epigastric discomfort in MI patients?

Answer 4

1) Dyspnea
2) Diaphoresis
3) Weakness, fatigue
4) Nausea and vomiting
5) Sense of impending doom
6) Syncope

Question 5

What is a complication of MI?

Answer 5

Sudden cardiac death - usually due to ventricular fibrillation (Vfib)

Question 6

How do you diagnose MI using ECG?

Answer 6

Markers for ischemia/infarction include:

1) Peaked T waves - occur very early and may be missed
2) ST segment elevation - indicates transmural injury and can be diagnostic of an acute infarct
3) Q waves - evidence for necrosis (specific) - q waves are usually seen late; typically not seen acutely
4) T-wave inversion is sensitive but not specific
5) ST segment depression: Subendocardial injury

Question 7

What two parts of a presentation strongly suggest acute MI?

Answer 7

1) The combination of substernal chest pain persisting for longer than 30 minutes
2) Diaphoresis

Question 8

How does right ventricular infarct present? What is it dependent on?

Answer 8

1) Inferior ECG changes
2) Hypotension
3) Elevated jugular venous pressure
4) Hepatomegaly
5) Clear lungs
6) Preload dependent - do NOT administer nitrates or diuretics as will cause cardiovascular collapse

Question 9

What percentage of the time does ST segment elevation indicate an infarction? What percentage of the time does ST segment depression indicate infarction?

Answer 9

1) 75% of the time

2) 25% of the time

Question 10

What ECG changes are expected in an anterior myocardial infarct and in what leads?

Answer 10

1) ST segment elevation in V1-V4 (acute/active)

2) Q waves in leads V1-V4 (late change)

Question 11

What ECG changes are expected in a posterior myocardial infarct and in what leads?

Answer 11

1) Large R wave in V1 and V2
2) ST segment depression in V1 and V2
3) Upright and prominent T waves in V1 and V2

Question 12

What ECG changes are expected in a lateral myocardial infarct and in what leads?

Answer 12

Q waves in leads I and aVL (late change)

Question 13

What ECG changes are expected in an inferior myocardial infarct and in what leads?

Answer 13

Q waves in leads II, III, aVF (late change)

Question 14

What are the two categories on infarcts?

Answer 14

1) ST segment elevation infarct: Transmural (involves entire thickness of wall); tends to be larger
2) Non-ST segment elevation infarct: Subendocardial (involves inner one-third to one-half of the wall); tends to be smaller, and presentation is similar to USA - cardiac enzymes differentiate the two

Question 15

What is the current diagnostic gold standard for myocardial injury?

Answer 15

Cardiac enzymes

Question 16

What is the most important enzyme test to order? When does it increase, peak, and return to normal?

Answer 16

1) Troponins (Troponin I and T)

2) Increases within 3 to 5 hours and returns to normal in 5 to 14 days; reaches a peak in 24 to 48 hours

Question 17

How does sensitivity and specificity for troponins differ from CK-MB? When should serum level of troponins be obtained? When can troponin I be falsely elevated?

Answer 17

1) Greater sensitivity and specificity than CK-MB for myocardial injury
2) Obtain serum levels of either troponin T or I on admission, and again every 8 hours for 24 hours
3) Troponin I can be falsely elevated in patients with renal failure; thus following trend of levels is important

Question 18

When does CK-MB increase, peak, and return to normal? When does it have the highest sensitivity and specificity? When should total levels be measured? When is it most helpful to measure?

Answer 18

CK-MB is less commonly used

1) Increases within 4 to 8 hours and return to normal in 48 to 72 hours; reaches a peak in 24 hours
2) When measured within 24 to 36 hours of onset of chest pain, has greater than 95% sensitivity and specificity
3) Levels of total CK and CK-MB should be measured on admission and every 8 hours thereafter for 24 hours
4) Most helpful in detecting recurrent infarction given quicker return to baseline than troponin

Question 19

When are cardiac enzymes drawn? What does a higher peak and longer enzyme level elevation indicate?

Answer 19

1) Cardiac enzymes are drawn serially - once on admission and every 8 hours until three samples are obtained
2) The higher the peak and the longer enzyme levels remain elevated, the more severe the myocardial injury and the worse the prognosis

Question 20

In MI, what agents are the only ones shown to reduce mortality?

Answer 20

1) Aspirin
2) Beta blockers
3) ACE inhibitors

Question 21

What forms of cardiac monitoring should be done for a patient with acute MI?

Answer 21

1) BP and HR: HTN increases afterload and thus oxygen demand, whereas hypotension reduces coronary and tissue perfusion. Both nitrates and morphine can cause hypotension
2) Rhythm strip with continuous cardiac monitor: Watch for dysrhythmias. Note that PVCs can lower stroke volume and coronary artery filling time. A high frequency of PVCs may predict VFib or VT
3) Auscultate the heart (third and fourth heart sounds, friction rub, and so on) and lungs (crackles may indicate LV failure, pulmonary edema)
4) Hemodynamic monitoring (CVP, PCWP, SVR, cardiac index [CI]) with a pulmonary artery catheter is indicated if the patient is hemodynamically unstable. Monitoring is helpful in assessing the need for IV fluids and/or vasopressors

Question 22

What are the three forms of treatment for acute MI?

Answer 22

1) Admit patient to a cardiac monitored floor (CCU) and establish IV access. Give supplemental oxygen and analgesics (nitrates, morphine)
2) Medical therapy
3) Revascularization
4) Rehabilitation

Question 23

What are forms of medical therapy for acute MI?

Answer 23

1) Aspirin
2) Beta blockers
3) ACE inhibitors
4) Statins
5) Oxygen
6) Nitrates
7) Morphine sulfate
8) Heparin

Question 24

How does aspirin help in MI treatment?

Answer 24

1) Antiplatelet agent reduces coronary reocclusion by inhibiting platelet aggregation on top of the thrombus
2) Has been shown to reduce mortality and should be part of long-term maintenance therapy

Question 25

How do beta blockers help in MI treatment?

Answer 25

1) Block stimulation of HR and contractility to reduce oxygen demand and decrease the incidence of arrhythmias
2) Reduce remodeling of the myocardium post-MI
3) Have been shown to reduce mortality and should be part of long-term maintenance therapy

Question 26

How do ACE inhibitors help in MI treatment?

Answer 26

1) Initiate within hours of hospitalization if there are no contraindications
2) Have been shown to reduce mortality and should be part of long-term maintenance therapy

Question 27

How do statins help in MI treatment? What did the PROVE IT-TIMI 22 trial show?

Answer 27

1) Reduce risk of further coronary events
2) Stabilize plaques and lower cholesterol
3) The PROVE IT-TIMI 22 trial showed the superiority of starting atorvastatin 80 mg over other statins before discharging a STEMI patient
4) Should be part of maintenance therapy

Question 28

How does oxygen help in MI treatment?

Answer 28

May limit ischemic myocardial injury

Question 29

How do nitrates help in MI treatment?

Answer 29

1) Dilate coronary arteries (increase supply)
2) Venodilation (decrease preload and thus demand)
3) Reduce chest pain, although not as effective as narcotics

Question 30

How does morphine sulfate help in MI treatment?

Answer 30

1) Analgesia

2) Causes venodilation, which decreases preload and thus oxygen requirements

Question 31

How does heparin help in MI treatment? What form of heparin is perferred and why?

Answer 31

1) Initiate in all patients with MI; prevents progression of thrombus; however, has not been shown to decrease mortality
2) LMWH, specifically enoxaparin, is preferred over unfractionated heparin, as shown in the ExTRACT TIMI 25 trial as well as a recent meta-analysis. Enoxaparin was shown to decrease the risk of another MI versus unfractionated heparin

Question 32

When is revascularization for MI most benefitial? When should it be considered?

Answer 32

1) Benefit highest when performed early (within 90 minutes of hospital arrival)
2) In all patients with MI

Question 33

What are options for revascularization?

Answer 33

1) Thrombolysis
2) PCI
3) CABG

Question 34

What are benefits of PCI over thrombolysis for MI? What should be chosen in patients with a delayed presentation?

Answer 34

1) Several studies have shown enhanced survival and lower rates of recurrent MI and intracranial bleeding when PCI performed by skilled personnel is chosen over thrombolysis
2) For patients with a delayed presentation, fibrinolysis alone may be a better option

Question 35

When is urgent/emergent CABG typically performed? When is it almost never performed?

Answer 35

1) Only in the setting of mechanical complications of an acute MI, cardiogenic shock, life-threatening ventricular arrhythmias, or after failure of PCI
2) It is almost never performed in the acute setting on a stable patient

Question 36

What word can be used to describe the effects of clopidogrel in the setting of aspirin? When should clopidogrel be used in the setting of revascularization? How long should dual antiplatelet therapy with aspirin and clopidogrel be continued for after a bare metal stent placement and after a drug-eluting stent?

Answer 36

1) Evidence suggests that benefits of clopidogrel is additive to the effects of aspirin
2) Clopidogrel therapy should be initiated in all patients who undergo PCI and receive a stent
3) Dual antiplatelet treatment with aspirin and clopidogrel should continue for at least 30 days in patients who receive a bare metal stent, and at least 12 months in patients who receive a drug-eluting stent

Question 37

What is cardiac rehabilitation? How does cardiac rehabilitation affect symptoms and survival?

Answer 37

1) Cardiac rehabilitation is a physician-supervised regimen of exercise and risk factor reduction after MI
2) Shown to reduce symptoms and prolong survival

Question 38

What did the CAPRICORN trial show?

Answer 38

It showed that the beta blocker carvedilol reduces risk of death in patients with post-MI LV dysfunction

Question 39

What medical treatments are indicated in patients with MI?

Answer 39

1) Oxygen
2) Nitroglycerin
3) Beta-blockers
4) Aspirin
5) Morphine
6) ACE inhibitor
7) IV Heparin

Question 40

What is the most helpful laboratory test to measure if patients have a recurrent infarction on the same hospital admission?

Answer 40

CK-MB is most helpful laboratory test to detect this if patient develops recurrent chest pain

Question 41

What is the preferred treatment for STEMI if it can be performed expeditiously and by skilled personnel? In what patients is it also preferred in?

Answer 41

1) Percutaneous Coronary Intervention, so long as it can be performed within 90 minutes (door to balloon time)
2) Also preferred in patients with contraindications for thrombolytic therapy; no risk of intracranial hemorrhage

Question 42

What did the PAMI trial show?

Answer 42

PAMI trial showed that PTCA reduces mortality more than t-PA

Question 43

When is thrombolytic therapy useful to use?

Answer 43

For patients who present later and for those in whom PCI is contraindicated

Question 44

When should thrombolytic therapy ideally be given?

Answer 44

Early treatment is crucial to salvage as much of the myocardium as possible

1) Administer as soon as possible up to 24 hours after the onset of chest pain
2) Outcome is best if given within the first 6 hours

Question 45

What is an indication for thrombolytic therapy?

Answer 45

ST segment elevation in two contiguous ECG leads in patients with pain onset within 6 hours who have been refractory to nitroglycerin

Question 46

What thrombolytic is the first choice? What are alternatives?

Answer 46

1) Alteplase has been shown to have the best outcomes amongst thrombolytic medications, and is the first choice in many centers, despite its high costs
2) Alternatives include streptokinase, tenecteplase, reteplase, lanoteplase, and urokinase

Question 47

What is the main reason to initiate therapy with thrombolytics/angioplasty in the ED setting?

Answer 47

Whether there is ST segment elevation on ECG

Question 48

What are absolute contraindications to thrombolytic therapy?

Answer 48

1) Trauma: Recent head trauma or traumatic CPR
2) Previous stroke
3) Recent invasive procedure or surgery
4) Dissecting aortic aneurysm
5) Active bleeding or bleeding diathesis

Question 49

How frequently is coronary artery bypass grafting (CABG) in comparison to PCI or thrombolytic therapy? What are benefits of CABG? When is it the procedure of choice?

Answer 49

1) Less often used than the other two in the acute setting
2) Benefits of CABG include low rates of event-free survival and reintervention-free survival
3) It remains the procedure of choice in patients with severe multivessel disease and complex coronary anatomy

Question 50

What are complication categories for acute MI?

Answer 50

1) Pump failure (CHF)
2) Arrhythmias
3) Recurrent infarction (extension of existing infarction or reinfarction of a new area)
4) Mechanical complications
5) Acute pericarditis
6) Dressler syndrome (“postmyocardial infarction syndrome”)

Question 51

What is the most common cause of in-hospital mortality?

Answer 51

Pump failure (CHF)

Question 52

If CHF is mild as a complication of acute MI, how is it treated? What may severe CHF as a complication of acute MI lead to? What may be indicated to do at this point?

Answer 52

1) Treat medically with ACE inhibitor and diuretic
2) May lead to cardiogenic shock
3) Invasive hemodynamic monitoring may be indicated

Question 53

What are the different types of arrhythmias that can develop post-MI?

Answer 53

1) Premature ventricular contractions (PVCs)
2) Atrial fibrillation (AFib)
3) Ventricular tachycardia (VT)
4) VFib
5) Accelerated idioventricular rhythm
6) Paroxysmal supraventricular tachycardia (PSVT)
7) Sinus tachycardia
8) Sinus bradycardia
9) Asystole
10) AV block

Question 54

How do you treat premature ventricular contractions (PVCs) post-MI?

Answer 54

Conservative treatment (observation) indicated; no need for antiarrhythmic agents

Question 55

How do you treat sustained ventricular tachycardia (VT)?

Answer 55

Sustained VT requires treatment: If patient is hemodynamically unstable, electrical cardioversion is indicated. If patient is hemodynamically stable, start antiarrhythmic therapy (IV amiodarone)

Question 56

How do you treat VFib?

Answer 56

Immediate unsynchronized defibrillation and CPR are indicated

Question 57

How do you treat accelerated idioventricular rhythm?

Answer 57

Does not affect prognosis; no treatment needed in most cases

Question 58

What may sinus tachycardia post-MI be caused by? Why is it bad to have? How do you treat it?

Answer 58

1) May be caused by pain, anxiety, fever, pericarditis, medications, etc.
2) Worsens ischemia (increases myocardial oxygen consumption)
3) Treat underlying cause (analgesics for pain, aspirin for fever, etc.)

Question 59

When does sinus bradycardia occur in relation to MI? Why may it be beneficial to have? What is the treatment?

Answer 59

1) A common occurrence in early stages of acute MI, especially right-sided/inferior MI
2) May be a protective mechanism (reduces myocardial oxygen demand)
3) No treatment is required other than observation. If bradycardia is severe or symptomatic (hemodynamic compromise), atropine may be helpful in increasing HR

Question 60

What is bad about asystole? How do you treat it? What if asystole is the cause of cardiac arrest?

Answer 60

1) Very high mortality
2) Treatment should begin with electrical defibrillation for VFib, which is more common in cardiac arrest and may be difficult to clearly differentiate from asystole
3) If asystole is clearly the cause of arrest, transcutaneous pacing is the appropriate treatment

Question 61

What is AV block associated with? What types of AV block do not require therapy?

Answer 61

1) Associated with ischemia involving conduction tracts

2) First-degree and second-degree (type I) blocks do not require therapy

Question 62

What is done for second degree (type II) and third degree heart blocks that can improve prognosis in the setting of an anterior MI? What about for inferior MI?

Answer 62

1) Prognosis is dire in the setting of an anterior MI - emergent placement of a temporary pacemaker is indicated (with later placement of a permanent pacemaker)
2) In inferior MI, prognosis is better, and IV atropine may be used initially. If conduction is not restored, a temporary pacemaker is appropriate

Question 63

What is a recurrent infarction?

Answer 63

1) Extension of existing infarction
or
2) Reinfarction of a new area

Question 64

What occurs to both short-term and long-term mortality in the setting of recurrent infarction?

Answer 64

Increased mortality

Question 65

Why is diagnosis often difficult in recurrent infarction? Are troponin levels useful to measure? Why may CK-MB be a good marker to detect recurrent infarction? What finding on EKG within the first 24 hours after infarction would make you suspect recurrent infarction?

Answer 65

1) Cardiac enzymes are already elevated from the initial infarction
2) Troponin levels remain elevated for a week or more, so are not useful here
3) CK-MB returns to normal faster, and so a reelevation of CK-MB after 36 to 48 hours may be due to recurrent infarction
4) If there is repeat ST segment elevation on ECG within the first 24 hours after infarction, suspect recurrent infarction

Question 66

What are mechanical complications of acute MI?

Answer 66

1) Free wall rupture
2) Rupture of interventricular septum
3) Papillary muscle rupture
4) Ventricular pseudoaneurysm
5) Ventricular aneurysm

Question 67

How severe is a free wall rupture post-MI and when does it occur? What is the mortality rate? What does it usually lead to? What is the treatment?

Answer 67

1) A catastrophic, usually fatal event that occurs during the first 2 weeks after MI (90% within 2 weeks, most commonly 1 to 4 days after MI)
2) 90% mortality rate
3) Usually leads to hemopericardium and cardiac tamponade
4) Treatment: Hemodynamic stabilization, immediate pericardiocentesis, and surgical repair

Question 68

How severe is a rupture of interventricular septum and what is the treatment? When does it usually occur? What is the likelihood of survival correlated to?

Answer 68

1) Greater potential for successful therapy than with a free wall rupture, although this is also a critical event; emergent surgery is indicated
2) Occurs within 10 days after MI
3) Likelihood of survival correlates with size of defect

Question 69

What does a papillary muscle rupture cause and how does this present? What test should be done is papillary muscle rupture is suspected? What treatment is needed?

Answer 69

1) Produces mitral regurgitation (presents with new murmur)
2) If suspected, obtain an echocardiogram immediately
3) Emergent surgery is needed (mitral valve replacement is usually necessary), as well as afterload reduction with sodium nitroprusside or intra-aortic balloon pump (IABP)

Question 70

What is a ventricular pseudoaneurysm? What test is best for detecting it? Why is it a surgical emergency?

Answer 70

1) Incomplete free wall rupture (myocardial rupture is contained by pericardium)
2) Bedside echocardiogram may show the pseudoaneurysm
3) Ventricular pseudoaneurysms tend to become a free wall rupture

Question 71

What types of ACS is heparin used for? What is it not used for?

Answer 71

1) Heparin is used for USA and MI (both NSTEMI and STEMI)

2) It is NOT used for stable angina

Question 72

What test should all patients initially treated conservatively for USA/NSTEMI undergo before leaving the hospital and why?

Answer 72

A stress test to determine the need for angiography (which in turn determines the need for angioplasty or CABG)

Question 73

Patients who suffer an acute MI have what level risk for a stroke during the next 5 years? What increases this risk?

Answer 73

1) High risk

2) The lower the EF and the older the patient, the higher the risk of stroke

Question 74

What is the most common cause of death in the first few days after MI?

Answer 74

Ventricular arrhythmia (either VT or VFib)

Question 75

After an MI, what should all patients be discharged home on?

Answer 75

1) Aspirin
2) Beta-blocker
3) Statins
4) ACE inhibitor

Question 76

What is a key difference between a complication of ventricular pseudoaneurysm and ventricular aneurysm? What are ventricular aneurysms associated with? What may be protective in the setting of a ventricular aneurysm? What treatment may be appropriate in selected patients?

Answer 76

1) Ventricular aneurysm rarely ruptures (in contrast to pseudoaneurysms)
2) Associated with a high incidence of ventricular tachyarrhythmias
3) Medical management may be protective
4) Surgery to remove aneurysm may be appropriate in selected patients

Question 77

What caused the incidence of acute pericarditis to decrease? What is the treatment? What medications are contraindicated and why?

Answer 77

1) The incidence has decreased sharply since the introduction of revascularization techniques
2) Treatment consists of aspirin (which is already standard in treatment of MI)
3) NSAIDs and corticosteroids are contraindicated (may hinder myocardial scar formation)

Question 78

What is Dressler syndrome (postmyocardial infarction syndrome)? What is the most effective therapy?

Answer 78

1) Immunologically based syndrome consisting of fever, malaise, pericarditis, leukocytosis, and pleuritis, occurring weeks to months after an MI
2) Aspirin. Ibuprofen is a second option