myocardial infarction Flashcards
What is the definition of myocardial infarction?
Necrosis of myocardium due to occlusion of a coronary artery (usually by thrombus following atherosclerotic plaque rupture) → interruption of blood supply.
Myocardial infarction is commonly referred to as a heart attack.
What triggers the pathophysiology of myocardial infarction?
Plaque rupture with subsequent platelet adhesion, aggregation, and thrombus formation + vasoconstriction triggered by thromboxane A2.
This leads to complete occlusion of the artery and transmural infarction.
What is the sequence of events leading to dyspnea in myocardial infarction?
MI → LV systolic dysfunction → increased blood in the LV → increased LV end-diastolic pressure → back pressures lead to increased LAP → increased PCWP exceeding oncotic pressure of plasma → leakage of fluid into the interstitium → dyspnea.
This illustrates how heart failure can lead to fluid buildup in the lungs, causing shortness of breath.
What are the clinical features of myocardial infarction?
Intense sub-sternal chest pain, diaphoresis, dyspnea, nausea & vomiting, sense of impending doom, syncope.
Pain may radiate to neck, jaw, left arm, or back and is not relieved by rest or nitroglycerin.
How can myocardial infarction present differently in certain populations?
May be asymptomatic in elderly, diabetics, or post-operative patients.
This can complicate diagnosis in these groups.
What heart sound is associated with acute coronary syndrome?
S4.
Ischemia is associated with non-compliance of the left ventricle.
What distinguishes STEMI from NSTEMI?
STEMI: Transmural involving entire wall thickness (ST-elevation); NSTEMI: Subendocardial involving inner 1/3 (ST-depression).
These terms describe the extent and type of myocardial injury.
What are common ECG findings in myocardial infarction?
Peaked T waves, Q waves, T-wave inversion, ST-elevation/depression.
These changes help in diagnosing the type and location of the MI.
Which leads indicate an inferior myocardial infarction?
II, III, aVF.
This indicates occlusion of the right coronary artery.
Which leads are associated with a lateral myocardial infarction?
I, aVL, V5, V6.
This is indicative of occlusion of the left circumflex artery.
What leads indicate an anterior myocardial infarction?
V3, V4.
This typically involves occlusion of the left anterior descending artery.
What is the gold standard for cardiac enzyme testing in myocardial infarction?
Troponin I and T and CK-MB.
Troponin is more sensitive and specific for myocardial injury.
What is a key feature of CK-MB in relation to recurrent myocardial infarctions?
CK-MB is useful for detecting recurrent infarctions because it returns to normal levels within 48-72 hours.
This makes it less useful for diagnosing a current MI but good for identifying past events.
Fill in the blank: Myocardial infarction is often caused by _______.
occlusion of a coronary artery due to thrombus formation.
This highlights the primary mechanism behind MI.
What is the first step in managing a patient with acute coronary syndrome?
Admit to the CCU & establish IV access
When should oxygen be administered to a patient with ACS?
If O2 is < 94%
What dual antiplatelet therapy is recommended for ACS?
Aspirin + clopidogrel
How long should dual antiplatelet therapy be continued after stenting or CABG?
First 6 months
What is the lifelong antiplatelet therapy after the initial dual therapy?
Aspirin for life
What medications are included in the initial treatment of ACS?
- Morphine
- Heparin
- Beta blocker
- Nitrate
- Statin
What is the recommended time frame for PCI in ACS management?
Door to balloon < 90 minutes
What is superior to tPA if available for ACS?
PCI
What is the recommended time frame for administering tPA?
Door to needle < 30 minutes, preferably within 6 hours
What is the treatment for NSTEMI regarding revascularization?
Not necessary immediately; may be treated initially with LMW heparin or GPIIb/IIIa inhibitors + angioplasty & stenting
What is the #1 cause of in-hospital mortality in ACS?
Heart failure
What complication is the #1 cause of death in the first few days post-MI?
Arrhythmias (ventricular arrhythmias)
List some mechanical complications of MI.
- Free wall rupture
- Interventricular septum rupture
- Papillary muscle rupture
- Ventricular pseudoaneurysm/aneurysm
What is Dressler syndrome?
Triad of fever, pericarditis + pleuritis, leukocytosis
How is Dressler syndrome treated?
Aspirin/ibuprofen
What are the signs of inferior MI associated with right ventricular infarction?
- 3rd degree heart block
- Hypotension
- Raised JVP with clear lung fields
What should be checked with a right lead ECG in inferior MI?
Right ventricular infarction
What is contraindicated in treating inferior MI with right ventricular infarction?
Nitrates
What causes acute LVH/pulmonary edema after MI?
- Multiple infarcts
- Recurrent infarcts
- Large infarcts
What is the management of acute pulmonary edema after MI?
- Propped up positioning
- Oxygen
- IV furosemide
- Morphine
- IV nitrate
- Inotropic support if poor LV function
- Intra-aortic balloon pump as a bridge prior to surgery
